Method of producing viscose having an opacifying agent



Patented July 25 1950 METHOD OF PRODUCING VISCOSE HAVING AN OPACIFYING AGENT Kenneth Russell Gray, Shelton, Wash., assignor to Rayonier Incorporated, Shelton, Wash., a

corporation of Delaware No Drawing. Application November 27, 1945, Serial No. 631,223

This invention relates to the production of cellulosic products and has for its general object the provision of certain improvements in carrying out one or more of the-processing'steps usedin the production of such products. The invention aims particularly to improve the emulsification or dispersion of non-miscible opacifying agents in a cellulosic solution used in spinning filaments, particularly as regards stabilizing emulsions produced in the presence of anion-active emulsifying materials. I

The invention contemplates the use of a cellulosic material to beprocessed into viscose which contains an oil-soluble material or composition that will lower the interfacial tension at an oilaqueous interface in the. resulting cellulosic solution due to adsorption of the material in the interface. Said material is more particularly described as being substantially non-volatile, insoluble in water or dilute caustic soda solution, soluble in oil, interiacially active at oil-water interrace, and unsaponifiable, and, for convenience, will hereafter be called unsaponifiable, oil soluble, interiacially active material.

In one of its important aspects, the invention 4 Claims. (Cl. 106-464) 2 manufacturing of rayon of producing a higher grade yarn.

We have previously found, however, that not all of the non-cellulosic impurities which can be removed are' undesirable, and in factcertain of such impurities, normally present in small amounts, act beneficially as emulsifying agents in the step of emulsifying or dispersing oils or pigments in the viscose. Thes beneficial impurities which act as emulsifying agents are surface active materials of the anion active class or materials which can give rise to the production of such surface active materials during the processing of pulp into viscose.-- In a pulp which has not been highly refined most of these beneficialimpurities constitute a portion of the materials removed by organic solvents, as for example, ether, benzene, alcohol, etc. These beneficial impurities which act as anion active emulsifying agents are of the involves the use of chemically prepared wood pulp (hereinafter called refined Wood pulp) as a source of cellulose in the preparation of cellulosic solutions tor the viscose and other processes in which extruded regenerated cellulose is produced, and has for a particular object the use of. an unsaponifiable, oil soluble, interfacially active material to improve emulsification. The invention also generally brings about improvements in other processing steps including spinning and may be used with bright as well as opacified viscose. The invention will, accordingly, be described with ref erence to the viscose process, it being understood that it is also applicable to other processes where aqueous cellulosic solutions are opacified or extruded into filaments or films.

Wood pulp as usually prepared as a source of cellulose for the viscose and related spinning industries is of various degrees of purity, and is generally supplied for use in the form of sheets. Normal dissolving Wood pulp in present use consists mainly of cellulose and contains an appreciable amount of non-cellulosic impurities, such as hemi-celluloses, fats, resins, waxes, etc. One of the main objects in-the manufacture of highly refined dissolving pulp is to remove as much as possible of the non-cellulosic impurities so that a whiter, purer pulp results which is capable in the nature of fats, oils, fatty acids, rosin and rosin acids, all of which become incorporated in the viscose as sodium soaps.

As used herein, the term anion active materials applies to' materials in the pulp which form soaps during steeping orageing as well as to addition of materials which areactually in an anion active form when in the pulp.

In the copending application oi Kenneth Russell Gray, Serial No. 601,063, filed June 22, 1945, the discovery is described in some detail that the ether extract includes an unsaponifiable material in the nature of high molecular weight alcohols, and especially sterols such as phytosterols, which are of a character entirely different from the soap-forming agents,

In theory, the problem of making a good pulp could be solved by removing all the undesirable impurities while retaining those impurities which facilitate the steps-of emulsification and other processing steps. Under such. theoretical conditions the impurities which. it would be desiredv to retain from the standpoint of emulsification would be: l

1) The natural oils, fats and fatty acids, rosin and rosin acids, which in the viscose process form soaps. Such soaps in addition to improving the processing of the pulp into viscose, also due to their presence in the viscose, act as emulsifying? agents.

(2) The natural interfacially active" materials soluble in oil and insoluble in water. Thesematerials are in the uns-aponifiable portion of the ether extractable matter and are mainly high molecular Weight alcohols,

In practice such a clean-cut separation i difiicult to accomplish directly. I have discovered that better results are obtainable by removing most or all of the impurities, including the unsaponifiable ether extractable matter, and then incorporating in the viscose small amounts of unsaponifiable, oil soluble, interfacially active material. Where the content of natural soapforming, emulsifying materials i low, anion active materials may also be added in accordance with Patent Re. 22,489, May 30, 1944.

In refined wood pulps, the unsaponifiable portion of the ether extractable matter will frequently fall below 0.07%. While our invention is particularly applicable to usein cellulosic solutions prepared from refined wood pulp containing not more than 0.07% ether extractable unsaponifiable material, and increasingly so as the material approaches zero, it may be applied with certain advantages to the processing of the refined wood pulps containing more than 0.0? of unsaponifiable, oil soluble, interfacially active material, although such pulps do not generally yield the highest grade yarns and their emulslons with oils are generally sufficiently stable for most purposes. With refined pulps containing less than 0.02% unsaponifiable material the advantages of adding the unsaponifiable, oil soluble, interfacially active material according to the invention are especially great.

In accordance with the invention, a small quantity of an unsaponifiable, oil soluble, interfacially active material stable in the pressure of dilute solutions of alkali metal hydroxide is incorporated in the cellulosic material used in producing the cellulosic solution, at least prior to completion of shredding the alkali cellulose, and preferably to the pulp prior to use, to improve the characteristics of the spinning solution, particularly with regard to emulsification.

Since the unsaponifiable, oil soluble, interfacially active materials are insoluble in water or dilute caustic soda they become dispersed in a fmely divided condition in the viscose. Since the materials are oil soluble they are thus in part extracted from suspension in the aqueous viscose phase by means of the oil droplets during the emulsification process. In order for this extraction process to take place to an efiicient degree it i not only necessary for the materials to be oil soluble, but also, that they be substantially water insoluble.

The unsaponifiable materials are compounds which we add in practicing our invention, like conventional surface active materials, are hydrophilic-lipophilic combinations. These compounds have a strong lipophilic group or groups, substantially of a hydrocarbon character, together with a group or groups having a relatively weak hydrophilic effect. Thus, the interfacially active unsaponifiable compounds used in my in a scum to separate.

vention are at least slightly oil soluble but sub-v phases. Nevertheless, when present at an oil water interface they produce very low interfacial tensions.

In general the unsaponifiable materials or compounds are high molecular weight alcohols, i. e., alcohols containing at least 10 carbon atoms. The alcohols may be aliphatic (straight or branched chain, saturated or unsaturated) or cyclic. They may be primary, secondary, or tertiary. The alcohols moreover may be either mono or dihydroxylic. I prefer to use high molecular weight cyclic alcohols and of these have found sterols to be particularly effective, especially phytosterols.

The following unsaponifiable compounds may be used in the practice of my invention:

1. Aliphatic monohydroxylic alcohols "n-oleyl, n-dodecyl, n-cetyl, n-stearyl alcohols.

5-ethylnonanol-2, 7-ethyl-Z-methylundecanol- 4 and 3,9-diethyltridecanol-6.

2. Aliphatic glycols Octadecanediol-l, l2. 3. C'ycZoaZiphat ic alcohols derived from rosin Dehydroabietyl, dihydroabietyl, tetrahydroabietyl, and abietyl alcohols. Mixtures of dihydroabietyl, dehydroabietyl, tetrahydroabietyl and abietyl alcohols of which one is sold under the trade name of Hydroabietyl alcohol.

4. Sterols and steroZ containing materials Phytosterols, stigmasterol, vsitosterol, ergosterol, alpha-tocopherol, cholesterol, lanolin, hemlock pulp ether extract unsaponifiables, spruce pulp ether extract unsaponifiables.

When viscose is emulsified with mineral oil,v

even if the oil particles are relatively fine, if the emulsions are not completely stable, there will bea tendency for the emulsions to cream or for In the viscose industry such scums are extremely troublesome in that they tend to collect in various lines and tanks and may work into the spinnerets where they will cause inferior or spoiled yarn. I have found that such scums tend to occur when the amount of ether extractable unsaponifiable material in the pulp is low, i. e., when such material is below 0.07% and especially when in the range of 0 to 0.02%. In such cases the scum will still be obtained even when anion active emulsifying agents are added to aid the emulsifying step.

A convenient laboratory test indicative of the relative amounts of scum obtainable in commercial operations with oil-opacified viscose from difierent pulp samples follows: 800 gm. of

viscose is emulsified for 5 minutes with 0.4% mineral oil based on viscose using a small bladed paddle revolving at 4000 R. P. M. Portions of the freshly emulsified viscose samples are then. centrifuged for 1 hour at a force of 1500 gravity..

The amounts of scum which may separate out as layers on the tops of the tubes from various viscose samples are compared. When the unsaponifiable material is added according to the invention topulps that would normally give scum in the above test, scum-is either complete-- 1y eliminated or greatly reduced. i

That scum formation is due to a lack of natural unsaponifiable ether extractable material may be seen from the following table. The table-alsow shows the remarkable effect on reduction of scum by addition of a small amount of phytosterol. i I i 7 I Effect on scam "in viscose emlul sions oj unsitpom'fiable and" sapomfiable portions o'f pulp eth'et f extractable matter and of an oil soluble, water insoluble, interfacially active additive (phytosterol) Amount of Natural Un- Amount of Natural Amount of Scum Pulp Used saponifiable EtherEx- SapouifiableEtherEx- Obtained in Scum tractable Material tractable Material Centrifuge Test #1 Pulp 0.034.. v 0.057.. Trace scum. #2 Pulp 0.013-. 0.065.. Heavy scum. #2 Pulp, Impreg. w1th 0.05% of Unsaponifiable Ether 0.013 natural +0.05% 0.065 Very small trace.

Extractable Material from #1 pu from #1 pulp. #2 Pulp Impreg. w th 0.05% of Saponifiable Ether 0.013 0.065 natural +0.05% Heavy Scum-addi- Extractable Materlal from #1 pulp. y from #1 pulp. tion having I no effect. #2 Pulp Impreg. with 0.03% of phytosterol 0.013 natural +0.03% Zero.

phytosterol.

The unsaponifi-able, oil soluble, interfacially active materials may be incorporated in the finished wood pulp, or during the formation of the pulp sheet or during the viscose processing, prior to the completion of shredding. Since the materials are not soluble in water it is not practical to add them directly to the viscose. Such direct addition gives an unsatisfactory distribution of the material in the viscose so that if the viscose is subsequently emulsified, the emulsion will not be satisfactorily stabilized. A most practical and convenient method of securing the presence of the desired amount of unsaponifiable material in the viscose in a satisfactorily fine state of subdivision is to incorporate the material in the wood pulp. Such an addition may be advantageously effected to the pulp on the sheet forming machine subsequent to sheet formation but prior to complete drying by spraying the pulp sheet with an aqueous emulsion or dispersion of the compound or by means of a rotating roll partly immersed in such an emulsion or dispersion. If desired, the unsaponifiable, oil soluble, interfacially active compounds may be incorporated in the pulp prior to sheet formation as, for example, by making additions to a suspension of pulp in water in a stock chest.

The application of the unsaponifiable materials or compounds to the pulp may be accomplished by use of a solution of the compound in a satisfactory organic solvent but more practically by use of an aqueous emulsion as described above. The preparation of such an aqueous emulsion may be efiected by any appropriate procedure common to the art, generally in the presence of a small amount of a water soluble emulsifying agent.

For application during the shredding operation, the compounds may be sprayed directly on to the alkali cellulose as a concentrated solution in a suitable organic solvent, preferably a Water miscible, volatile solvent such as ethyl alcohol or isopropanol. They may also be sprayed into the shredder as a concentrated emulsion or liquid compounds may be employed in undiluted form.

We have also discovered that esters of the aforementioned unsaponifiable alcohols which decompose in the presence of caustic soda may be likewise used since they liberate the unsaponifiable compounds during the steeping and aging periods and thus in effect add the free alcohol to the alkali cellulose prior to completion of shredding. The esters used may be either water insoluble or soluble. An example of a soluble ester which may be used is disodium monolauryl sulfosuccinate. This compound has the advantage of being water soluble and decomposes either periods and thus in effect. adds lauryl alcohol to the alkali cellulose prior to the completion of shredding. Similarly in place of an emulsion of oleyl alcohol there may be used a water solution of disodium mono oleyl sulfosuccinate.

Where the ether extract of the pulp is very low, in addition to adding the unsaponifiablc, oil soluble, interfacially active material, anion active compounds may be added according to Patent No. Re. 22,489. In such cases it will frequently be convenient to emulsify the unsaponifiable material in a solution of the anion active compound to be also added, Anion active compounds especially suited to be used in combination with the unsaponifiable compounds are the sodium salts of fatty and resin acids.

While the unsaponifiable compounds are especially suitable for use in combination with anion active compounds, they are also suitable for use in combination with cation active compounds, non ionic surface active compounds and mixture of these.

With highly refined pulp, as the ether extractable material approaches zero, if only the unsaponifiable, oil soluble, interfacially active compounds are added Without anion active compounds some improvements are obtained but the advantages of the invention are obtained only in part. In the preferred form of the invention anion active compounds will be present, either through their presence in natural form in the ether extractable material or by addition.

While pulp treated with an unsaponifiable compound is especially suited for the preparation of viscose which is to be opacified with oil, such treated pulp may be also used with advantage in the preparation of bright viscose or in the preparation of viscose opacified with non-oleaginous materials.

When viscose is emulsified with oil for the preparation of delustered rayon, the oil constitutes only a very small portion of the delustered material. Accordingly since the unsaponifiable compounds dissolve in the oil rather than in the aqueous phase only extremely small quantities of them are required, the effective range of the compounds being from 0.01 to 0.07% and preferably from 0.02 to 0.05%. Since the unsaponifiable materials or compounds are not truly soluble in the viscose but rather disperse, with more than 0.07 of such materials, some material may tend to separate out in the viscose, particularly with bright viscose. Accordingly it is important that the compounds be added only in extremely small amounts. The percentages used herein are based on the bone dry weight of the pulp.

I claim:

1. In the production of viscose having an opacifying agent dispersed therein the improvement largely or wholly during the steeping and aging hich comprises shredding alkali cellulose formed of wood pulp having ether extractable saponifiv droxyl substituted hydrocarbon being a sterol.

able and unsaponifiable matter therein, the unsaponifiable matter being water insoluble, oil soluble, interfacially active and consisting of a portion naturally present in the pulp and a portion added as an hydroxyl substituted hydrocarbon selected from the group consisting of an aliphatic hydroxyl substituted hydrocarbon having at least 10 carbon atoms and a cycloaliphatic hydroxyl substituted hydrocarbon having at least 10 10 carbon atoms, the total amount of unsaponifiable matter not exceeding 0.07% based on the bone dry weight of the wood pulp, whereby in the subsequent processing into viscose said opacifying agent is dispersed in the viscose without objectionable scum formation.

2. In the method of claim 1, the added by- REFERENCES CITED The following references are of record in the file of this patent:

v UNITED STATES PATENTS Numb er Name Date 2,066,385 Barthelemy Jan. 5, 1937 2,234,626 Bredee Mar. 11, 1941 

1. IN THE PRODUCTION OF VISCOSE HAVING AN OPACIFYING AGENT DISPERSED THEREIN THE IMPROVEMENT WHICH COMPRISES SHREDDING ALKALI CELLULOSE FORMED OF WOOD PULP HAVING ETHER EXTRACTABLE SAPONIFIABLE AND UNSAPONIFIABLE MATTER THEREIN, THE UNSAPONIFIABLE MATTER BEING WATER INSOLUBLE, OIL SOLUBLE, INTERFACIALLY ACTIVE AND CONSISTING OF A PORTION NATURALLY PRESENT IN THE PULP AND A PORTION ADDED AS AN HYDROXYL SUBSTITUTED HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF AN ALIPHATIC HYDROXYL SUBSTITUTED HYDROCARBON HAVING AT LEAST 10 CARBON ATOMS AND A CYCLOALIPHATIC HYDROXYL SUBSTITUTED HYDROCARBON HAVING AT LEAST 10 CARBON ATOMS, THE TOTAL AMOUNT OF UNSAPONIFIABLE MATTER NOT EXCEEDING 0.07% BASED ON THE BONE DRY WEIGHT OF THE WOOD PULP, WHEREBY IN THE SUBSEQUENT PROCESSING INTO VISCOSE SAID OPACIFYING AGENT IS DISPERSED IN THE VISCOSE WITHOUT OBJECTIONABLE SCUM FORMATION. 